Smoke filters



April 24, 1962 R. A. 'WHITMORE SMOKE FILTERS Filed Jan. 8, 1958 Inventor Robert A. W/zz'imore United States Patent Ofi ice 3,030,964 Patented Apr. 24, 1962 3,030,964 SMOKE FHJEERS Robert A. Whitmore, Beverly, Mass., assignor to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey Filed Jan. 8, 1958, Ser. No. 707,736 22 Claims. (Cl. 131-40) This invention relates to a smoke filter and filtering process and particularly to a filter and process for th treatment of tobacco smoke.

Reports suggesting harmful results from smoking tobacco have led to the insertion of filters in cigarettes and other smoking articles. Cigarette smoke is an aerosol, i.e. a suspension in air of spherical, semi-solid particles of tars, nicotine and other materials, and it is these particles which the filters are employed to remove. A variety of filter materials have been proposed, including paper and cellulose acetate fiber in various forms and configurations. The filters interpose in the path of the smoke a mass of fibers with small intervening spaces. It has been considered that the density of the mass of fibers and the smallness of the intervening spaces blocked and trapped smoke particles much in the fashion of a sieve to reduce the quantity of all suspended materials drawn through the filter. Efforts towards improving filtration have been directed to arranging the fibrous matter to provide more effective mechanical blocking and trapping of smoke particles. Often these filters are made so dense, in the attempt to remove a high portion of harmful components, that they offer substantial resistance to the passage of all gases and vapors. The net result of this filtering action is often a thin, relatively fiavorless smoke, and frequently a hard drawing cigarette or other smoking article.

It is an object of the present invention to provide a free drawing, inexpensive smoke filter and smoke filtering process which, by reason of the chemical and physicochemical character of the filter employed, is particularly effective for the improvement of smoke from tobacco in such articles as cigarettes, cigars, and pipes.

The suspended semi-solid particles of tars and nicotine of cigarette smoke are extremely small so that the mechanical filtering or trapping action employed in conventional cellulosic fiber smoke filters leaves much to be desired. Since the smoke particles are so much smaller than the passageways through filter material, the removal of smoke particles according to the present invention is achieved by providing a fibrous mass designed to cause deposition of smoke particles on the fibers rather than to act as a sieve. To this end applicant has provided a filter comprising a mass of fibers in which the fibers are arranged for bringing smoke particles against surfaces of the fibers, and he has selected a material which physically presents large irregular surface areas available for deposition of smoke particles and which chemically and physico-chemically readily accepts and firmly retains smoke particles impinging on the surfaces.

The smoke filter system of the present invention provides a filter component of irregular surfaced fibers of highly absorbent collagen fibers alone or with other fibers assembled together in a passageway for smoke to provide a path insuring turbulent'flow. These irregular surfaced fibers provide a multitude of impingement surfaces for removing solid particles from the smoke. and a very large specific surface area particularly effective for contact with the smoke to remove undesirable components. It has been founddesirable to employ collagen material in a chemically treated state having reduced water absorbing activity, stability on storage and in use, and controlled hydration.

Passage of tobacco smoke through a free-drawing filter formed of these collagen fibers removes a very high portion of undesirable components from the smoke.

The invention will be described further in connection with the drawings forming part of the disclosure of the present invention.

In the drawings:

FIG. 1 is an angular view with parts broken away of a cigarette including a smokefilter according to the present invention;

FIG. 2 is a section on a larger scale taken on the line 11-11 of FIG. 1 and showing a portion of the smoke filter; and

FIG. 3 is an angular view with parts broken away showing a smoking pipe with a smoke filter according to the present invention disposed in the smoke passage.

In a cigarette 10 (see FIG. 1) smoke from the burning tip portion 12 of the tobacco is drawn back through the mass 14 of unburned tobacco in the paper cylinder 16 defining the body of the cigarette. The mass 14 of unburned tobacco is a porous shredded cellulosic material and acts in very much the same way as do the common cellulose fiber filters in cigarette tips to remove moisture and tar and solid particles through the physical processes of absorption of moisture and mechanical entrapment of particles.

After passing through the mass 14 of tobacco, the

smoke passes through the filter 18. As shown on enlarged scale in FIG. 2, the filter 18 comprises a mass of collagen fibers within the paper cylinder. The fibers are disposed to provide passages for the smoke between and around the fibers for removal of undesired components. Various arrangements of fibers may be used such as random mass, a mass in which the fibers are substantially axially arranged, a twisted tow and so on. The fibers of the filter are packed firmly enough for convenience in assembly and stability in the cigarette, but the fibers used according to the present invention are so eflicient that dense packing is not required.

- The filtering of cigarette smoke is not merely a matter of passing smoke through a fine sieve to strain out particles, for the interstices between the fibers or other structure of the filter are very much larger than the smoke particles. Filtering of smoke involves disposing the filter material to insure a type of fiow which will cause smoke particles to impinge against and deposit on surfaces of the filter material. Three factors appear to be involved, namely, arrangement of the filter material to insure bringing smoke particles against surfaces of the filter material, the provision of a large surface area of filter material available to receive smoke particles and providing a filter material having a high degree of acceptance and retention of smoke particles impinging thereon.

Cellulosic fibers such as cellulose acetate fibers are smooth surfaced, and possess no special chemical or physical attraction for smoke particles. Collagen fibers, on the other hand, have a naturally irregular configuration such that when assembled in a mass they provide a multiplicity of irregular passageways which are highly effective to cause turbulent fiow of smoke passing therethrough. This turbulent flow insures good impingement of smoke particles on surfaces of the filter material.

Collagen fibers are known to have an extremely high specific area, is. ratio of surface area to weight of material. For example, the specific area has been calculated by J. K. Kanagy in the Journal of American Leather Chemists Association, vol. 42, page 98, for 1947, as 298 square meters per gram; and the specific area may be substantially higher than this. This high specific area is a significant advantage in giving a large surface area per unit volume of filter material on which smoke particles may deposit.

The mechanism governing the deposit and retention of smoke particles upon a surface is not entirely clear. The highly polar character of the surface of the collagen fibers seems to be an important factor in the specific effectiveness of these fibers for treating tobacco smoke. Two mechanisms have been suggested which may account for the extremely effective removal of smoke particles by protein fibers according to the present invention. One of these mechanisms is based on electrostatic charge on smoke particles. On page 410 of Applied Colloid Chemistry, by Bancroft, published 1932 by McGraw-Hill Book Co., Inc., it is stated that, In ordinary smokes about 30% of the particles are charged electrically. Protein fibers are amphoteric. These fibers, in the form in which they are used in filters, still contain approximately to of water, and in effect are dry to the touch electrolytes. It is known that the electric charge on suspensoidal particles is in some measure responsible for the stability of the suspension and that neutralization of the charges of the particles will result in coagulation and deposition of the particles. It is believed that the charge neutralizing action of the collagen fibers on the charged smoke particles is at least in part responsible for the improved smoke particle removing action of the protein fibers over such essentially dry insulating fiber type filter materials as cellulose or cellulose derivative filter materials.

A second mechanism involves the chemical activity of the protein fibers. That is, while cellulose, the base material of conventional filters, is a polymer constituted of glucoside residue units presenting only active hydroxyl groups, collagen fibers are constituted of a complex combination of amino acid units providing a large number of polar groups, specifically amine and carboxyl groups for action and reaction with aldehydes, acids, and other constituents of tobacco smoke. This active surface of the collagen fibers is believed to combine chemically with the smoke components referred to and to bind them rapidly so that they are not free to re-enter the stream of smoke and gases and pass through the filter.

The above mechanisms are offered only to aid in understanding the unusually effective action of the collagen fiber filter. Validity of the claims, however, is not based on the correctness of either or both of the proposed mechanisms but on the novelty and advantages of smoke filtering with the collagen fiber filter.

The collagen fibers making up the present filter may be derived from any of a number of sources including skin or hide material, bone, tendon or other connective tissue, partially detanned leather scrap, fibers reconstituted from dissolved collagen, or mixtures of these alone or with other fibers.

Reduction of the source material to fiber state will depend on the source selected. Invention in the present case is not predicated on the procedure employed in reducing the source material to fibers.

In order to provide chemical and physical stability for the collagen fibers, both for safety in storage and for maximum efficiency in use, a chemical treatment is desirable in their preparation. This chemical treatment, which may be of the nature of a light tannage, such as an aldehyde tannage or a light acid bath tannage of mineral tanning agents such as chromium, aluminum, zirconium, or iron tannage, the polyphosphate tanning agents, or even a vegetable tannage, retards or prevents hydration and swelling of the fibrous material. The treated fiber will contain from 0.5% to 2.5% by Weight of aldehyde or from 0.5% to 1.5% by weight of the mineral tanning agents expressed as their oxides, the weight percent being based on the dry weight of the fiber. It therefore does not develop a gluey surface or become a soggy mass when subjected to the condition of high humidity and high temperature developed in the process of smoking. This treatment also has a preservative action and prevents the occurrence of putrefaction in storage.

The preparation of chemically treated collagen fibers from skin or hide for use as a smoke-filtering medium may follow a portion of the method used in preparing collagen fibers in a previous application entitled Collagen Fiber Masses and Methods of Making the Same, Serial No. 691,728, filed October 22, 1957, now US. Patent No. 2,934,447, in which I am a co-inventor. Useful skin or hide materials for reduction to fibers include various waste products from packing houses and tanneries such as a limed unhaired hide, pickled hide, unlimed hide, or hide scraps or trimmings. As described more fully in the above referred to application, the skin or hide material is washed if necessary and its pH is brought to between about 7 and about 11, if it is not already in this range, by soaking in an aqueous solution containing base or acid depending on the pH correction needed.

Chemical treatment, e.g. limited formaldehyde tanning, is most simply carried out by immersing the skin or hide material, after adjustment to a pH of 7 to 11, in an aqueous bath containing formaldehyde until the skin or hide material has taken up the formaldehyde from solution. The treatment with formaldehyde is carried out under conditions which will give a combined aldehyde content of from about 0.5 to about 2.5% by weight based on the weight of the collagen fibers. This may be accomplished, for example, by leaving the skin or hide material overnight in a 1% formaldehyde aqueous solution at pH 10.5; but other conditions may be employed in accordance with known aldehyde treatment techniques. Comparable modification of the collagen may be obtained with other aldehydes such as glyoxal (suitably in a 3% aqueous solution at pH 7.8 to 11) or p-quinone (suitably in a A aqueous solution at pH of 7.8 to 11).

As described in the referred to application, this treated material is cut into pieces, mixed with water, and is then beaten to separate the material into fibers. These fibers are mechanically separated from suspension in water as by skimming.

Optionally, the skimmed off fibers are dewatered, resuspended in water, and using an acidifying agent such as phosphoric acid, the pH is adjusted to an equilibrium pH of 2.5 to 6.5, preferably about 3.5 to 5.5. The suspension is allowed to stand overnight at this pH.

The fibers, whether acidified or not, are then separated from the suspension, drained and dried, preferably by solvent or freeze-drying techniques. A suitable solvent drying system may utilize first a bath of acetone and then of isopropanol. The solvent is removed from the dried material by passing it through squeeze rolls or centrifuge, and the residue solvent removed by evaporating in air. The solvent or freeze dried fibers may then be flufied and opened using, for example, a carding device.

It is possible to dry the fibers without solvent or freeze drying techniques by putting the drained water-wet fibers in a carding device and carding until the fibers are dry.

The resultant product is a white, soft, fluffy, fibrous material, with high specific area, good absorption, a high concentration of reactive sites for removing undesirable components, and non-allergenic properties.

An alternative collagen fibrous material may be prepared by partially detanning chrome tanned leather scrap to reduce its chrome content below about 1.5%. This may be done by reducing the leather to finely divided fibrous state, for example in a paper beater and immersing the fibers in successive baths of aqueous oxalic acid solution. This treatment removes a substantial portion of the chrome and changes the color of the fibers from the blue to substantially white. The effect of removing chrome is to reduce the possibility of toxicity from the chrome in the fibers and to free active groups of the collagen for reaction with aldehydes and tannins in tobacco smoke.

The fibrous collagen material is formed into cylindrical bodies by suitable means and short sections of this body are disposed in the end portions of cigarettes as cigarette filters. In the cylindrical bodies the fibers may extend in generally the same direction or may extend w heterogeneously, or the entire body may be twisted to provide a somewhat helical arrangement of the fibers. However, the specific arrangement of the fibers is not of critical importance since the collagen fibers are extremely effective agents for the removal of components from tobacco smoke.

If desired, the cylindrical bodies may be made up of blends of fibers which have been acidified as described above with alkaline collagen fibers prepared without the acidifying treatment. In these blends there is some evidence indicating that the acidified fiber reacts with tannins and nicotine in the smoke while the alkaline fibers react more effectively with aldehyde components. The collagen fibers, whether acid, alkaline or blended, may also be combined with suitable other fibrous material, for example, with a small proportion of cellulose acetate fibers to give greater strength and ease of handling to the cylindrical body from which the filler plugs are cut.

Where mixtures of acid equilibrated and alkali equilibra-ted collagen fibers are employed the relative proportions will depend upon the relative amounts of aldehydes, tars or nicotines that it is desired to remove to provide a smoke of determined optimum composition. Observable differences in component-removing action are obtainable where as little as of one of these collagen fibers is combined with the other. That is, desirable combined fiber compositions will include acid equilibrated fibers and alkali equilibrated fibers in the range of relative proportions of from 1:10 to 10:1.

The smoking pipe shown in FIG. 3 comprises a bowl for the tobacco to be burned, a stem portion 22 of the bowl, and a bit 24 having a reduced portion 26 fitting into a matching recess 28 in the stem 22 of the pipe. A smoke passage 30 extends from the bowl 20 to the end 32 of the bit 24 through which smoke from burning tobacco is drawn. This passageway 30 has an enlarged portion 34 partly in the stem 22 and partly in the bit 24 in which a filter plug 36 of collagen fibers is disposed. In the course of smoking a pipe containing this filter plug, the collagen fibers of the filter plug discolor rapidly showing efiective removal of components from the tobacco smoke.

This description is not intended to limit the use of this material to filters for cigarettes or pipes. It is suitable for use in any smoking article as a medium to remove physiologically harmful ingredients contained in any tobacco smoke Without impairing flavor.

, The following example is given to aid in understanding the invention and it is to be understood that the invention is not restricted to the particular materials, conditions, or proportions recited in the example:

Example I Fifty (50) lbs. of limed split hide trimmings were washed in a drum for 15 minutes in cold running tap water and then allowed to stand in tap water for 30 minutes. 7 At this point the pH of the material was 10.2. The trimmings were drained and were then drummed for 30 minutes in a mixture comprising 30 gal. of water and 2850 ml. of 37% formalin. After drumming the material was allowed to stand in the formalin solution for 24 hrs.

. The material was again drained and then cut into 1" squares. The squares were run through the sharp hobbed plates of a Bauer mill, three passes with 0.4 clearance between theplates, two passes at 0.3" clearance, and two passes at 0.2 clearance. The resulting mixture or fibrous suspension had a solids content of about 1012%.

Two liters of this fibrous suspension were placed in a Hollander. with four liters of water and beaten for 30 minutes, with a close setting of .001 to .005 clearance between blades and bed plates. The suspension was then drained on a screen and the fibers were passed between squeeze rolls. The fibers were then placed in an 0.001 molal phosphoric acid bath and brought to an equilibrium pH of 3.8 by adding successive small portions of phosphoric acid and letting it equilibrate between additions. Afiter reaching a pH of 3.8, the suspension was allowed to stand overnight.

The fibrous suspension was then drained on a screen and the fibers were passed between rubber squeeze rolls. The squeezed fibers were placed in six liters of dry acetone and allowed to stand with agitation for one hour. The fibers were then drained and passed between squeeze rolls. This fibrous material was then placed in dry isopropanol and allowed to stand with occasional agitation for one hr., then drained and passed through squeeze rolls. The material, damp with volatile isopropanol, was hand-carded until dry.

From the dried fibers prepared as above, there was prepared a wad 9 mm. in diameter and 15 mm. long and weighing 47.3 mgs. This wad was substituted for the filter in a commercial filter cigarette. After smoking, the wad was removed and weighed. It was then allowed to dry in air at room temperature for 24 hrs. and was then weighed again. A filter cigarette of the same brand containing its own filter was smoked and the filter weighed directly after smoking and after drying. The results were as follows:

The weight of material after drying which was extracted or removed from tobacco smoke by the collagen filter is nearly four times that of the commercial filter which itself weighs four times the collagen filter. This indicates the efliciency of the collagen fibers is approximately 16 times per unit weight greater than that of the commercial filter material.

Example ll One hundred parts by Weight of chrome tanned leather shavings were introduced into 5000 parts by weight of water in a paper heater and beaten for one hr. to reduce the shavings to finely divided fibers. The fibers were separated from water by screening and immersed for periods of from four to five hrs. in successive baths of aqueous 5% oxalic acid solution. The immersion in each bath was followed by draining on a screen and passing the screened fibers between rubber squeeze rolls. After five baths the color of the fibers was no longer blue but was substantially white; and the fibers had a chrome content of 1.4% (expressed as C-r O by weight of the fibers. The drained and squeezed fibers from the last bath were placed in two par-ts by volume of dry acetone and allowed to stand with agitation for one hr. The fibers were then drained and passed between squeeze rolls. This fibrous material was placed in dry isopropanol and allowed to stand with occasional agitation for one hr, then drained and passed through squeeze rolls. The material, damp with volatile isopropanol was hand-carded until dry. The dried fibers were employed as filter plugs in cigarettes and were found effective to remove a substantial proportion of components from cigarette smoke.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

'1. A tobacco smoke filtering system comprising surfaces defining a passageway for said smoke and a mass 'Z of naturally irregularly surfaced fine fibers of collagen disposed in said passageway, said fibers being associated with each other and with the surfaces of said passageway to define tortuous paths for said smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up material from said smoke.

2. A tobacco smoke filtering system for removing harmful ingredients from tobacco smoke comprising surfaces defining a passageway for said smoke and a mass of naturally irregularly surfaced fine fibers of collagen disposed substantially to fill a cross section of said passageway, said collagen fibers being chemically treated to improve their stability and control their hydration, said fibers being associated with each other and with the surfaces of said passageway to define tortuous paths for said smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up material from said smoke.

3. In combination, a body of tobacco to be burned, surfaces defining a passageway for drawing smoke from burning portions of said body of tobacco through the remainder of said body of tobacco and a mass of naturally irregularly surfaced fine fibers of collagen disposed in said passageway substantially to fill a cross section of said passageway, said fibers being associated with each other and with the surfaces of said passageway to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up components from said smoke and said collagen fibers being lightly tanned to improve their stability and control their hydration.

4. A cigarette comprising a cylindrical body of tobacco, a cylindrical filter unit adjacent one end of the tobacco and in alinement therewith and substantially of the same diameter as the body of tobacco, and a burnable paper wrapping around the tobacco and the filter unit, said filter unit comprising a mass of naturally irregularly surfaced fine fibers of collagen associated with each other and with the wrapping to define tortuous paths for smoke from said tobacco through said mass, the surfaces of said fibers providing a large number of active sites for taking up components from said smoke and said collagen fibers being lightly tanned to improve their stability and control their hydration.

5. In combination, a body of tobacco to be burned, surfaces defining a passageway for drawing smoke from burning portions of said body of tobacco through the remainder of said body of tobacco and a mass of naturally irregularly surfaced fine fibers of collagen disposed in said passageway substantially to fill a cross section of said passageway, said fibers being associated with each other and with the surf-aces of said passageway to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up components from said smoke and said collagen fibers being combined with 0.5% to 2.5% by Weight of an aldehyde based on the weight of the fibers to improve their stability and control their hydration.

6. In combination, a body of tobacco to be burned, surfaces defining a passageway for drawing smoke from burning portions of said body of tobacco through the remainder of said body of tobacco and a mass of naturally irregularly surfaced fine fibers of collagen disposed in said passageway substantially to fill a cross section of said passageway, said collagen fibers being combined with 0.5 to 2.5 by weight of an aldehyde based on the weight of the fibers, said mass comprising a mixture of acidic collagen fibers equilibrated at a pH of from about 2.5 to 6.5 and alkaline collagen fibers equilibrated at a pH of from about 7 to about 11, said fibers being associated with each other and with the surfaces of said passageway to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up tannins, nicotine and aldehydes from said smoke.

7. A cigarettecomprising a cylindrical body of tobacco, acylindrical filter unit adjacent one end of the tobacco and in alinement therewith and substantially of the same diameteras'the body of tobacco, and a burnable paper wrapping around the tobacco and the filter unit, said filter unit comprising a mass of naturally irregularly surfaced fine fibers of collagen associated with each other and with the wrapping to define tortuous paths for smoke from said tobacco through said mass, said collagen fibers being combined with from 0.5% to 2.5% by weight of an aldehyde based on the weight of the fibers, said mass comprising a mixture of acidic collagen fibers equilibrated at a pH of 2.5 to 6.5 and alkaline collagen fibers equilibrated at a pH of from about 7 to about 11, the surfaces of said fibers providing a large number of active sites for taking up tannins, nicotine and aldehydes from said smoke.

8. In combination, a body of tobacco to be burned, surfaces defining a passageway for drawing smoke-from burning portions of said body of tobacco through the remainder of said body of tobacco and a mass of naturally irregularly surfaced fine fibers of collagen disposed in said passageway substantially to fill a cross section of said passageway, said fibers being associated with each other and with the surfaces of said passageway to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a -large number of active sites for taking up components from said smoke and said collagen fibers being combined with 0.5% to 1.5% by weight, calculated as its oxide, of a mineral tanning agent based on the weight of the fibers to improve their stability and control their hydration.

9. In combination, a body of tobacco to be burned, surfaces defining a passageway'for drawing smoke from burning portions of said body of tobacco through the remainder of said body of tobacco and a mass of naturally irregularly surfaced fine fibers of collagen disposed in said passageway substantially to fill a cross section of said passageway, said fibers being associated with each other and with the surfaces of said passageway to define tortu-i ous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up components from said smoke and said collagen fibers being combined with from about 0.5% to about 1.5% by weight of chromium calculated as Cr O based upon the weight of the fibers to improve their stability and control their hydration.

10. A method for treating tobacco smoke which comprises passing the smoke through a mass of naturally irregularly'surfaced fine fibers of collagen, said fibers being associated with each other to define tortuous paths for smoke through said mass and the surfaces of said fibers providing a large number of active sites for taking up components of said smoke.

11. A method for treating tobacco smoke which comprises passing the smoke from a burning portion of a body of tobacco through the unburned portion of said body and thereafter passing the smoke through a mass of naturally irregularly surfaced fine fibers of collagen, said fibers being associated with each other to define tortuous paths for smoke through said mass and the surfaces of said fibers providing a large number of active sites for taking up components of said smoke, said collagen fibers being lightly tanned to improve their stability and control their hydration.

12. A method for treating tobacco smoke to remove harmful components which comprises passing the smoke from a burning portion of a body of tobacco through the unburned portion of said body and thereafter passing the smoke through a mass of naturally irregularly surfaced fine fibers of collagen, said fibers being associated with each other to define tortuous paths for smoke through said mass and the surfaces of said fibers providing a large number of active sites for taking up components of said smoke, said collagen fibers being combined with 0.5%

to 2.5% by weight of an aldehyde based on the weight of the fibers to improve their stability and control their hydration.

13. A method for treating tobacco smoke to remove harmful components which comprises passing the smoke from a burning portion of a body of tobacco through the unburned port-ion of said body and thereafter passing the smoke through a mass of naturally irregularly surfaced fine fibers of collagen, said collagen fibers being combined with 0.5% to 2.5% by weight of an aldehyde based on the weight of the fibers, said mass comprising a mixture of acidic collagen fibers equilibrated at a pH of from about 2.5 to 6.5 and alkaline collagen fibers equilibrated at a pH of from about 7 to about 11, said fibers being associated with each other to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up tannins, nicotine and aldehydes from said smoke.

14. A method for treating tobacco smoke to remove harmful components which comprises passing the smoke from a burning portion of a body of tobacco through the unburned portion of said body and thereafter passing the smoke through a mass of naturally irregularly surfaced fine fibers of collagen, said fibers being associated with each other to define tortuous paths for smoke through said mass and the surf-aces of said fibers providing a large number of active sites for taking up components of said smoke, said collagen fibers being combined with from 0.5% to 1.5% by weight, calculated as its oxide, of a mineral tanning agent based on the Weight of the fibers to improve their stability and control their hydration.

15. A method for treating tobacco smoke to remove harmful components which comprises passing the smoke from a burning portion of a body of tobacco through the unburned portion of said body and thereafter passing the smoke through a mass of naturally irregularly surfaced fine fibers of collagen, said fibers being associated with each other to define tortuous paths for smoke through said mass, the surfaces of said fibers providing a large number of active sites for taking up components from said smoke and said collagen fibers being combined with from about 0.5 to about 1.5 by weight of chromium calculated as Cr G based upon the weight of the fibers to improve their stability and control their hydration.

16. The improved method of treating tobacco smoke resulting from the combustion of tobacco during the act of smoking, comprising bringing the tobacco smoke between the burning tobacco and the mouth of the smoker, into contact with collagen whereby noxious substances of the tobacco smoke are selectively absorbed.

17. The improved method of treating tobacco smoke resulting from the combustion of tobacco during the act of smoking, comprising bringing the tobacco smoke between the burning tobacco and the mouth of the smoker, into contact with collagen fibers whereby noxious substances of the tobacco smoke are selectively absorbed.

18. A filter cigarette having a filter positioned therein to require substantially all smoke that may be drawn from a lighted tip thereof to the opposite tip thereof to pass therethrough, said filter containing substantially pure collagen.

19. A filter tip cigarette having a filter element consisting at least in part of substantially pure collagen.

20. A filter tip cigarette having a filter element consisting at least in part of substantially pure collagen fibers.

21. In a cigarette having a filter, the improvement in the filter which comprises the presence therein of an effective amount of collagen.

22. In a cigarette having a filter, the improvement in the filter which comprises the presence therein of an effective amount of collagen fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,552,129 Windus May 8, 1951 2,883,990 Nichols Apr. 28, 1959 FOREIGN PATENTS 606,427 Great Britain Aug. 13, 1948 755,479 Great Britain Aug. 22, 1956 

16. THE IMPROVED METHOD OF TREATING TOBACCO SMOKE RESULTING FROM THE COMBUSTION OF TOBACCO DURING THE ACT OF SMOKING, COMPRISING BRINGING THE TOBACCO SMOKE BETWEEN THE BURNING TOBACCO AND THE MOUTH OF THE SMOKER, INTO CONTACT WITH COLLAGEN WHEREBY NOXIOUS SUBSTANCES OF THE TOBACCO SMOKE ARE SELECTIVELY ABSORBED. 